To provide a movable throttle valve capable of preventing an annular gap from being clogged with dusts in operation fluid while being simple construction.

The movable throttle valve 5 used in a fluid pressure circuit 10 has a holding condition for holding a position of a piston in a cylinder and a tubular passage Qa (T) for releasing operation fluid expanding along with the temperature change in the holding condition, a throttle valve body 1 can reciprocally move in the throttle valve passage 2 by a pressure acting on the throttle valve body 1 even though the fluid pressure circuit 10 is in the holding condition, openings 1a, 1d to the tubular passage Qa (T) are arranged in a part for housing the throttle valve body 1 of the throttle valve passage 2 or a part outside more than the part for housing the throttle valve body 1.